#!/usr/bin/env perl

use strict;

# On-the-fly urxvt font resizing.  Like ⌘{+,-}, on mac computers
#
# Noah K. Tilton <noahktilton@gmail.com>
#
# What it does:
#
# 1) Emits escape sequences to change the font size in the running console;
# 2) Persists the changed font size to xresources file.
#
# Note: the regexes will only work on xft xrdb entries
#
# References: man 3 urxvtperl

use constant X_RESOURCES => "~/.Xresources";

sub change_size
{
  my ($self, $cmd) = @_;

  my (@pieces)  = split /:/, $self->{term}->resource("font");   # TODO make boldFont work
  my (@resized) = ();

  foreach my $piece (@pieces)
  { 
    if ($piece =~ /pixelsize=(\d*)/)
    {
      my $size      = $1;
      my $new_size  = (($cmd =~ m/font:increment/) ? ($size+1) : ($size-1));
      $piece =~ s/pixelsize=$size/pixelsize=$new_size/;
    }
    push @resized, $piece;
  } 

  my ($resized_str)   = join (":", @resized);
  my $UPDATE_STR      = "urxvt\*"      . $case . ":" .  $resized_str . "\n";
  my $SAVE_STR        = "xrdb -edit " . X_RESOURCES;
  my $RESIZE_STR      = "\033]50;"    . $resized_str . "\007";
  my $LOAD_STR        = "xrdb -load " . X_RESOURCES;

  system($LOAD_STR);                                          # load the xrdb db
  open(XRDB_MERGE, "| xrdb -merge") || die "can't fork: $!";
  local $SIG{PIPE} = sub { die "xrdb pipe broke" };
  print XRDB_MERGE $UPDATE_STR;                               # merge the new values
  close XRDB_MERGE || die "bad xrdb: $! $?";
  system($SAVE_STR);                                          # write the db values back to the file
  $self->{term}->cmd_parse($RESIZE_STR);                      # update the urxvt runtime
}

sub on_user_command
{
  # This function is called whenever some urxvt.keysym.*: perl:x:y
  # mapped in X_RESOURCES is called; where x is this "module" (file,
  # translation unit...), y is some function in this file (and this
  # function, if defined), and $cmd is the argument z.
  #
  my ($self, $cmd) = @_;
  if ($cmd =~ /font:..crement/) { $self->change_size($cmd); }
}